Hey all,


Thanks in advance for the help. Here's everything that I know and that I've tried. The heater in my navigator isn't "working", as in it never gets hot. I know these cars have issues with the blend door, but I don't have symptoms that lead me to believe that's the issue. (I can feel the air pressure change and hear the airflow change as I adjust the temp setting). Next, I've checked the coolant level (in the overflow only) and will be checking the radiator tomorrow. I've also felt the heater hoses (both leading to the heater core and coming out of the top of the radiator). Heater core hoses were warm, but not hot. Top radiator hose was about the same, and was not pressurized. The heater control valve, on the heater hose, is not being actuated by vacuum (I assume the line is broken somewhere behind the dash as I checked it inside the engine compartment).


OK...So...I know these things are wrong: 1. The heater control valve. Not sure which way is open/closed. But I've tested this component is both orientations and still had no heat (I zip tied it the actuated direction to test my theory). 2. Potentially the thermostat. I used my laser thermometer on the heater hoses and got a high temp of around 120, low in the 90's, much cooler than full operating temp, leading me to believe it's perhaps the thermostat. Also, with the upper hose never being pressurized, it could mean that the thermostat is stuck open??? 3. Radiator cap. Perhaps the more appropriate reason that the upper hose is not pressurized. After checking the overflow tank at "full" operating temp, it was slightly pressurized when I removed the cap.


I hoping that someone will have better knowledge of the cooling system than I gained tonight while working on it. My next steps are to check the radiator coolant level, check the radiator cap, check the thermostat housing temp with my laser thermometer, and that's about all I can think of.


Please let me know if you have ANY ideas that I can try. The last thing I want to do it tear our the dash to replace the heater core and blend door when that could potentially not fix my issue.


Again, thanks for all the help. It was a high of 22 today, thankfully the heater seats still kinda work.


Shane

 

If you're getting 120 degree water to the hot water valve you should feel at least SOME heat coming out of your vent outlets if you ask for it. When you ask for cold air, vacuum is applied to the hot water valve to close it. When you ask for warm air the vacuum is taken away and the hot water valve opens and allows water flow. So with the engine running and you asking for warm air you should see no vacuum at the water valve and it's arm is extended opening the water valve. When you ask for cold air from the vents you should see full vacuum at the water valve and it's arm retracted, closing the water valve to cut off water flow. But yes, you should see at least 180 degrees there at the thermostat housing if it's controlling coolant temps correctly.


-Mike

 

Your first step is to change the t-stat.

 

The easiest way to isolate the valve from the control system is to simply disconnect the vacuum line from the valve and plug that line while testing. With no vacuum applied, the integral spring should keep the valve open and allow a continuous flow of hot coolant through the core, assuming the rest of the system is working correctly.

Follow alloro's advice above. Until your coolant is HOT, you won't be able to get adequate heat until mid-July.

 

On our 2003 Exped 5.4L when you turn the temp selector to cold, select the A/C button to on and have the vent control set to anything other than "MAX A/C" the heater control valve remains open with no vacuum applied.

 

On a manual HVAC system, the valve is supposed to be closed only in the MAX A/C position.

The Navigator has either the EATC or the DATC, not a manual control. The control of the valve is done by the software in the control unit and should respond however the deign engineer set it up, there's no cut and dried situation where it's going to be activated, the software will is probably set up to optimize system performance.